1. Field of the Invention
The present invention relates to a pliable plastic film which can maintain a function of an easily releasable sealed portion even after a sterilization treatment at a high temperature of higher than 120° C., and a container using the same.
2. Description of the Related Art
Recently, a multichamber container, which separately contains a plurality of components and is capable of mixing the components in the container when used, is used in the medical field such as infusion solution bag.
The multichamber container comprises a plastic container having pliability, and a plurality of chambers which are partitioned with a so-called easily releasable sealed portion, and the seal strength of the easily releasable sealed portion is adjusted so that the easily releasable sealed portion is released when a pressure is applied by pressing the chamber.
The easily releasable sealed portion is usually formed by heat sealed films made of a mixture of two or more kinds of resins which are inferior in compatibility and have different melting points. A container used in the medical field such as an infusion solution bag is formed by using a resin mixture of polyethylene and polypropylene which have established safety to the human body and stability to medicines (see, for example, Japanese Patent No. 2,675,075).
However, in a medical container containing hyperalimentation solution, peritoneal dialysis fluid, perfusate, irrigation water for surgical operation or the like, sterilization at a high temperature of 120° C. or higher is sometimes required. In such a case, a sterilization treatment temperature exceeds a melting point of polyethylene, and there arise problems such as deformation of the container and increase in the peel strength of the easily releasable sealed portion as a result of the sterilization treatment.
On the other hand, Japanese Unexamined Patent Publication No. 2000-5276 proposes a multichamber container in which an innermost layer constituting the easily releasable sealed portion of the container is formed of a mixture of a syndiotactic polypropylene having a crystalline melting point Tm of 121 to 140° C. and polypropylene having an isotactic pentad fraction of 0.96 or less and a crystalline melting point Tm of 140 to 160° C. for the purpose of maintaining the function of the easily releasable sealed portion even if a sterilization treatment is carried out at 120° C. or higher.